Light-Initiated Continuous Flow Degradation of Per- or Polyfluoroalkyl Substances (PFAS)

Rachael K. Matthews, Cameron J. Shearer

Chemistry Department, College of Sciences, Adelaide University, Australia

 

PFAS

C–F bonds are resistant to biodegradation and current chemical destruction

 

Photolysis

H_2 O ↔┴UV H^∙+〖OH〗^∙

H_2 O ↔┴UV  e_aq^-+ H^++〖OH〗^∙

 

Photocatalysis

Self-cleaning surfaces, water purification, air sterilization and green hydrogen production are current examples of photolysis and photocatalysis

 

Photolysis at low pH

27 ppm F- can be produced at pH < 3

Conditions: [PFOA]0 = 100 ppm, batch, 2 mL, 275 nm UV LED array (40-50 mW/cm2), HCl, 24 h, n = 1-7

Analysis: F NMR, F- ISE

 

Other acids & F mass balance

Conditions: [PFOA]0 = 100 ppm, batch, 2 mL, 275 nm UV LED array (40-50 mW/cm2), 24 h, n = 1-7

Analysis: F NMR, F- ISE, LC-HRMS

HCl, H2SO4, HBr & HOCl are capable of acid-mediated photolysis, but HNO3 inhibits F- production

Other organic F is produced (e.g. short-chain PFAS), and some F is left unaccounted for

 

AgTaO3

AgTaO3 metal oxides have a 3.4 eV bandgap which is sufficient for C–F bond reduction

 

Photoreduction of PFOS

F- production only observed in presence of triethanolamine (hole scavenger)

100 % PFOS conversion, 75 % mineralization

Conditions: [PFOS]0 = 50 or 100 ppm, batch, 2 mL, 365 nm UV LED array (510 mW/cm2), hole scavenger (TEOA), 24 h, n = 1

Analysis: F NMR, F- ISE, LC-HRMS

 

Continuous circulating flow

 

Mineralization under flow conditions

Photocatalytic reduction of PFOS demonstrated in continuous circulating flow system

> 80 % PFOS mineralization observed

Conditions: [PFOS]0 = 100 ppm, flow, 10 mL, 365 nm UV LED array (764 mW/cm2), 48 h circulation, 15.3 h interaction, n = 1

Analysis: F NMR, F- ISE

 

Matthews et. al. Chem. Mater. 2025.

Matthews et. al. Colloids Surf. A Physicochem. Eng. Asp. 2026.

Hamza et. al. Small 2025.

Toyota et. al. ACS Appl. Nano Mater. 2026.